The present invention relates to a numerical control system having a memory capable of permanently storing an edited program with ease on the part of a user.
FIG. 1 of the accompanying drawings is a block diagram of a conventional numerical control system (hereinafter referred to as an "NC system") having an editing capability. In FIG. 1, a machining program in the form of an NC language is stored on an NC tape (or a cassette tape). The NC system includes an input unit 2 containing a readout circuit, a command interpreter circuit, and other circuits, a control unit 3, a memory 4, a processing unit 5, a setting and display unit 6 including a keyboard and a display such as CRT, and an output unit 7. Designated at 8 is a new edited machining tape (or a cassette tape).
The NC system with an editing capability of the above construction is used as follows: Based on the machining program loaded from the NC tape through the input unit 2, the processing unit 5 performs necessary processing operations under the control of the control unit 3. Resultant processed data are then temporarily stored in a RAM region 4A of the memory 4, and are edited by operating on the setting and display unit 6 normally using a high-level language such as BASIC. An edited program as a result of such editing operation is stored in the RAM region 4A.
The data on the edited program are then successively read out of the RAM region 4A through the output unit 7 for controlling a machine tool or for delivery to another NC system. When it is desired to store the edited program permanently, the signals delivered through the output unit 7 are punched into the NC tape 8 or stored in the cassette tape.
Since the edited program is stored in the RAM region in the conventional NC system, the edited program cannot be stored permanently within the NC system. Permanent storage of the edited program should therefore be made on the NC tape 8 (or cassette tape). Therefore, a tape puncher or a magnetic recording unit is required. Storage of the edited program in the RAM region is disadvantageous in that the stored program may inadvertently be destroyed through an error of the operator. When the power supply for the NC system is kept off for a long period of time, the stored edited program is erased and hence will not be available for use. Where the edited program is stored on the NC tape 8 or the cassette tape, it has to be loaded again into the RAM region for use, resulting in a time-consuming procedure. Storage of the edited program on ROM card requires a device for writing the program into a separate ROM.